Power tools such as nut runners, drills, grinders, sanders or similar type tools frequently provide a rotating shaft at a given speed and torque. Depending on the function being performed, it is often advantageous to provide a rotating shaft at variable speeds and variable torques. The speed and torque of a rotating shaft may be altered through the use of gears and motors. For example, when using a power tool to rotate a fastener, it is often desirable to rotate the fastener at a high rate of speed throughout the fastening process until the fastener is almost tightened or meeting with additional resistance. During final tightening or increased resistance, it is often advantageous to apply a low speed rotation with a higher torque. The speed and torque of the output shaft of a power tool may be altered by engaging and disengaging various gears.
Disadvantages of known power tools providing a rotating shaft may include the use of motors that are restricted to air or pneumatic motors only. Some types of power tools may only provide output torques at discrete or pre-defined output torque levels. Other disadvantages include the use of motors requiring extensive maintenance and lubrication. Still other disadvantages may include inadvertent shifting from high speed/low torque output to a low speed/high torque output rotation before such a shift is desired. Additionally, some devices may require the use of relatively long, torque transmitting shafts for transmitting rotational motion through a relatively long, hollow shaft which may create numerous disadvantages. A disadvantage of such arrangements is that more material may be required thus adding increased weight and cost to the power tool. Finally, some devices do not allow for the adjustment of gear ratios to pre-select or adjust the desired output speed and torque of the output shaft.